Technical Abstract:
Adopting proper management practices for poultry litter (PL) is critical for increased N efficiency to maximize yield and to reduce negative environmental impacts. This three year study investigated effects of application time (fall and spring), and tillage (surface broadcast and soil incorporation) of three PL rates and NH4NO3 (145.6 kg N ha-1) on selected soil nutrient availabilities and corn (Zea mays L.) grain yield in Sand Mountain, AL. The target plant available N rates of the poultry litter were 67.5 kg N ha-1 (low rate), 135.0 kg N ha-1 (medium rate) which is similar to the NH4NO3 rate and 270.0 kg N ha-1 (high rate), doubled the medium rate. Poultry litter application time and tillage responses were measured by means of grain yield, grain nutrient uptake, and soil inorganic N, mehlich-3P (M-3P) and available K which were measured in April, mid-season (June/July) and post-harvest (Oct./Nov.). All PL rates and NH4NO3 regardless of application time and tillage significantly corn grain yield. Grain yield from the high PL rate regardless of application time was similar to the medium PL rate when spring applied. The Medium PL rate resulted in 600 kg ha-1 greater grain yield than NH4NO3 from both spring and fall applications. Incorporating fertilizer sources increased grain yield compared to surface broadcast only from the medium PL rate (590 kg ha-1) and the NH4NO3 (480 kg ha-1). Soil inorganic N, M-3P and available K, were greatest for all fertilizer sources from mid-season sampling, and generally greater from spring compared to fall applications whether or not the differences were significant. At the end of the study, Inorganic N, M-3P and available K, increased by 438%, 91% and 75% respectively. Grain uptake of N, was greater from spring than fall applied poultry litter when all but low PL rate was applied, but P and K were affected similarly from both fall and spring applications of all fertilizer treatments. When fertilizers were incorporated, the medium PL rate resulted in greater uptake of N and P; NH4NO3 in greater K from spring than fall applications.